1. Field of the Invention
Exemplary aspects of the present invention relate to a fixing device and an image forming apparatus, and more particularly, to a fixing device for fixing a toner image on a recording medium and an image forming apparatus incorporating the fixing device.
2. Description of the Related Art
Related-art image forming apparatuses, such as copiers, facsimile machines, printers, or multifunction printers having at least one of copying, printing, scanning, and facsimile functions, typically form an image on a recording medium according to image data. Thus, for example, a charger uniformly charges a surface of an image carrier; an optical writer emits a light beam onto the charged surface of the image carrier to form an electrostatic latent image on the image carrier according to the image data; a development device supplies toner to the electrostatic latent image formed on the image carrier to render the electrostatic latent image visible as a toner image; the toner image is directly transferred from the image carrier onto a recording medium or is indirectly transferred from the image carrier onto a recording medium via an intermediate transfer member; a cleaner then cleans the surface of the image carrier after the toner image is transferred from the image carrier onto the recording medium; finally, a fixing device applies heat and pressure to the recording medium bearing the toner image to fix the toner image on the recording medium, thus forming the image on the recording medium.
The fixing device installed in such image forming apparatuses may include a fixing roller and an opposed pressing roller that apply heat and pressure to a recording medium bearing a toner image. For example, the pressing roller is pressed against the fixing roller heated by a heater to form a fixing nip therebetween through which the recording medium bearing the toner image is conveyed. As the fixing roller and the pressing roller rotate and convey the recording medium through the fixing nip, they apply heat and pressure to the recording medium, melting and fixing the toner image on the recording medium.
Thereafter, the recording medium bearing the toner image is discharged from the fixing nip toward the outside of the fixing device. However, the recording medium may adhere to the fixing roller due to an adhesive force of the toner image heated by the fixing roller. To address this circumstance, a separation pawl may be located at an exit of the fixing nip to separate the recording medium from the fixing roller. Since the separation pawl is also designed to contact and guide the recording medium to the outside of the fixing device, the separation pawl has a side effect of producing scratches on the toner image on the recording medium.
To address this problem, a guide roller may be disposed in proximity to the separation pawl to guide the recording medium separated from the fixing roller by the separation pawl toward the outside of the fixing device.
However, immediately after the recording medium is discharged from the fixing nip, the recording medium still stores heat conducted from the fixing roller, softening the toner image thereon. While the recording medium moves from the separation pawl to the guide roller, it comes into contact with the separation pawl and the guide roller. Hence, as the recording medium slides over the separation pawl and the guide roller, the separation pawl and the guide roller may scratch the softened toner image on the recording medium, thus producing scratches and glossy streaks on the toner image.
Additionally, as the recording medium conveyed through the fixing nip is applied with heat and pressure, moisture contained in the recording medium may be evaporated and adhered to an interior wall of a conveyance path through which the recording medium discharged from the fixing nip is conveyed as water droplets. When the water droplets move to the recording medium, they may be left as water droplet marks on the recording medium.